The Sample Acquisition Core will provide a centralized efficient mechanism for providing the clinical materials needed for the research protocols of each of the individuals research projects included in this program. The common focus on immunologic mechanisms in rheumatoid arthritis shared by each of the individual projects lends itself well to a unified effort to identify and recruit potential subjects, to handle the blood, synovial fluid, and synovial membrane samples obtained from the subjects, and to apportion them as needed to each of the investigators. The director of the core in consultation with the principal investigators of each of the component projects will establish the criteria for selection of patients with rheumatoid arthritis for entry into this study and will educate the Nurse Clinical Coordinator in identifying appropriate candidates by screening of the medical record. The Nurse Clinical Coordinator will attend the outpatient activities of the Division of Rheumatology and screen medical records to identify those patients meeting entry criteria and register them in a computerized database of potential research candidates. As patients are needed for research, their physician will be contacted for approval and the Nurse Clinical Coordinator or the Core Director will then attempt to recruit the patient for the studies. The Nurse Clinical Coordinator will draw the required blood specimens form those patients who agree to participate and the patient's physician or the Core Director will perform arthrocenteses for those patients donating synovial fluid. The Nurse Clinical Coordinator will process the blood and synovial fluid specimens, contact the individual investigators, and arrange for delivery of the samples to the research laboratories. For those projects requiring correlation between rheumatoid disease activity and research laboratory findings, quantitative joint examinations will be performed by the Nurse Clinical Coordinator and/or the Core Director.